2 * Copyright (C) 1995-2007 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief Reassociation
23 * @author Michael Beck
32 #include "irgraph_t.h"
36 #include "iropt_dbg.h"
39 #include "reassoc_t.h"
45 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
47 typedef struct _walker_t {
48 int changes; /**< set, if a reassociation take place */
49 waitq *wq; /**< a wait queue */
53 NO_CONSTANT = 0, /**< node is not constant */
54 REAL_CONSTANT = 1, /**< node is a Const that is suitable for constant folding */
55 REGION_CONST = 4 /**< node is a constant expression in the current context,
56 use 4 here to simplify implementation of get_comm_Binop_ops() */
60 * returns whether a node is constant ie is a constant or
61 * is loop invariant (called region constant)
63 * @param n the node to be checked for constant
64 * @param block a block that might be in a loop
66 static const_class_t get_const_class(ir_node *n, ir_node *block)
68 ir_op *op = get_irn_op(n);
73 /* although SymConst's are of course real constant, we cannot
74 fold them, so handle them like region constants */
75 if (op == op_SymConst)
79 * Beware: Bad nodes are always loop-invariant, but
80 * cannot handled in later code, so filter them here.
82 if (! is_Bad(n) && is_loop_invariant(n, block))
86 } /* get_const_class */
89 * returns the operands of a commutative bin-op, if one operand is
90 * a region constant, it is returned as the second one.
92 * Beware: Real constants must be returned with higher priority than
93 * region constants, because they might be folded.
95 static void get_comm_Binop_ops(ir_node *binop, ir_node **a, ir_node **c)
97 ir_node *op_a = get_binop_left(binop);
98 ir_node *op_b = get_binop_right(binop);
99 ir_node *block = get_nodes_block(binop);
100 int class_a = get_const_class(op_a, block);
101 int class_b = get_const_class(op_b, block);
103 assert(is_op_commutative(get_irn_op(binop)));
105 switch (class_a + 2*class_b) {
106 case REAL_CONSTANT + 2*REAL_CONSTANT:
107 /* if both are constants, one might be a
108 * pointer constant like NULL, return the other
110 if (mode_is_reference(get_irn_mode(op_a))) {
118 case REAL_CONSTANT + 2*NO_CONSTANT:
119 case REAL_CONSTANT + 2*REGION_CONST:
120 case REGION_CONST + 2*NO_CONSTANT:
129 } /* get_comm_Binop_ops */
132 * reassociate a Sub: x - c = x + (-c)
134 static int reassoc_Sub(ir_node **in)
137 ir_node *right = get_Sub_right(n);
138 ir_mode *rmode = get_irn_mode(right);
141 /* cannot handle SubIs(P, P) */
142 if (mode_is_reference(rmode))
145 block = get_nodes_block(n);
148 * convert x - c => x + (-c)
150 if (get_const_class(right, block) == REAL_CONSTANT) {
151 ir_node *left = get_Sub_left(n);
156 switch (get_const_class(left, block)) {
158 irn = optimize_in_place(n);
168 /* already constant, nothing to do */
171 mode = get_irn_mode(n);
172 dbi = get_irn_dbg_info(n);
174 /* Beware of SubP(P, Is) */
175 irn = new_rd_Minus(dbi, current_ir_graph, block, right, rmode);
176 irn = new_rd_Add(dbi, current_ir_graph, block, left, irn, get_irn_mode(n));
178 DBG((dbg, LEVEL_5, "Applied: %n - %n => %n + (-%n)\n",
179 get_Sub_left(n), right, get_Sub_left(n), right));
192 /** Retrieve a mode from the operands. We need this, because
193 * Add and Sub are allowed to operate on (P, Is)
195 static ir_mode *get_mode_from_ops(ir_node *op1, ir_node *op2)
199 m1 = get_irn_mode(op1);
200 if (mode_is_reference(m1))
203 m2 = get_irn_mode(op2);
204 if (mode_is_reference(m2))
210 } /* get_mode_from_ops */
213 * reassociate a commutative Binop
215 * BEWARE: this rule leads to a potential loop, if
216 * two operands are region constants and the third is a
217 * constant, so avoid this situation.
219 static int reassoc_commutative(ir_node **node)
222 ir_op *op = get_irn_op(n);
223 ir_node *block = get_nodes_block(n);
226 get_comm_Binop_ops(n, &t1, &c1);
228 if (get_irn_op(t1) == op) {
230 const_class_t c_c1, c_c2, c_t2;
232 get_comm_Binop_ops(t1, &t2, &c2);
234 /* do not optimize Bad nodes, will fail later */
238 c_c1 = get_const_class(c1, block);
239 c_c2 = get_const_class(c2, block);
240 c_t2 = get_const_class(t2, block);
242 if ( ((c_c1 > NO_CONSTANT) & (c_t2 > NO_CONSTANT)) &&
243 ((((c_c1 ^ c_c2 ^ c_t2) & REGION_CONST) == 0) || ((c_c1 & c_c2 & c_t2) == REGION_CONST)) ) {
244 /* All three are constant and either all are constant expressions or two of them are:
245 * then applying this rule would lead into a cycle
247 * Note that if t2 is a constant so is c2 hence we save one test.
252 if ((c_c1 != NO_CONSTANT) /* & (c_c2 != NO_CONSTANT) */) {
253 /* handles rules R7, R8, R9, R10:
254 * convert c1 .OP. (c2 .OP. x) => x .OP. (c1 .OP. c2)
256 ir_node *irn, *in[2];
257 ir_mode *mode, *mode_c1 = get_irn_mode(c1), *mode_c2 = get_irn_mode(c2);
259 /* It might happen, that c1 and c2 have different modes, for instance Is and Iu.
262 if (mode_c1 != mode_c2) {
263 if (mode_is_int(mode_c1) && mode_is_int(mode_c2)) {
264 /* get the bigger one */
265 if (get_mode_size_bits(mode_c1) > get_mode_size_bits(mode_c2))
266 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
267 else if (get_mode_size_bits(mode_c1) < get_mode_size_bits(mode_c2))
268 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
270 /* Try to cast the real const */
271 if (c_c1 == REAL_CONSTANT)
272 c1 = new_r_Conv(current_ir_graph, block, c1, mode_c2);
274 c2 = new_r_Conv(current_ir_graph, block, c2, mode_c1);
282 mode = get_mode_from_ops(in[0], in[1]);
283 in[1] = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
286 mode = get_mode_from_ops(in[0], in[1]);
287 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
289 DBG((dbg, LEVEL_5, "Applied: %n .%s. (%n .%s. %n) => %n .%s. (%n .%s. %n)\n",
290 c1, get_irn_opname(n), c2, get_irn_opname(n), t2,
291 t2, get_irn_opname(n), c1, get_irn_opname(n), c2));
293 * In some rare cases it can really happen that we get the same node back.
294 * This might be happen in dead loops, were the Phi nodes are already gone away.
305 } /* reassoc_commutative */
307 #define reassoc_Add reassoc_commutative
308 #define reassoc_And reassoc_commutative
309 #define reassoc_Or reassoc_commutative
310 #define reassoc_Eor reassoc_commutative
313 * Reassociate using commutative law for Mul and distributive law for Mul and Add/Sub:
315 static int reassoc_Mul(ir_node **node)
318 ir_node *add_sub, *c;
321 if (reassoc_commutative(&n))
324 get_comm_Binop_ops(n, &add_sub, &c);
325 op = get_irn_op(add_sub);
327 /* handles rules R11, R12, R13, R14, R15, R16, R17, R18, R19, R20 */
328 if (op == op_Add || op == op_Sub) {
329 ir_mode *mode = get_irn_mode(n);
330 ir_node *irn, *block, *t1, *t2, *in[2];
332 block = get_nodes_block(n);
333 t1 = get_binop_left(add_sub);
334 t2 = get_binop_right(add_sub);
336 /* we can only multiplication rules on integer arithmetic */
337 if (mode_is_int(get_irn_mode(t1)) && mode_is_int(get_irn_mode(t2))) {
338 in[0] = new_rd_Mul(NULL, current_ir_graph, block, c, t1, mode);
339 in[1] = new_rd_Mul(NULL, current_ir_graph, block, c, t2, mode);
341 mode = get_mode_from_ops(in[0], in[1]);
342 irn = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
344 /* In some cases it might happen that the new irn is equal the old one, for
346 * (x - 1) * y == x * y - y
347 * will be transformed back by simpler optimization
348 * We could switch simple optimizations off, but this only happens iff y
349 * is a loop-invariant expression and that it is not clear if the new form
351 * So, we let the old one.
354 DBG((dbg, LEVEL_5, "Applied: (%n .%s. %n) %n %n => (%n %n %n) .%s. (%n %n %n)\n",
355 t1, get_op_name(op), t2, n, c, t1, n, c, get_op_name(op), t2, n, c));
367 * The walker for the reassociation.
369 static void wq_walker(ir_node *n, void *env)
371 walker_t *wenv = env;
373 set_irn_link(n, NULL);
374 if (is_no_Block(n)) {
375 ir_node *blk = get_nodes_block(n);
377 if (is_Block_dead(blk) || get_Block_dom_depth(blk) < 0) {
378 /* We are in a dead block, do not optimize or we may fall into an endless
379 loop. We check this here instead of requiring that all dead blocks are removed
380 which or cf_opt do not guarantee yet. */
383 waitq_put(wenv->wq, n);
384 set_irn_link(n, wenv->wq);
389 * The walker for the reassociation.
391 static void do_reassociation(walker_t *wenv)
397 while (! waitq_empty(wenv->wq)) {
398 n = waitq_get(wenv->wq);
399 set_irn_link(n, NULL);
401 blk = get_nodes_block(n);
402 if (is_Block_dead(blk) || get_Block_dom_depth(blk) < 0) {
403 /* We are in a dead block, do not optimize or we may fall into an endless
404 loop. We check this here instead of requiring that all dead blocks are removed
405 which or cf_opt do not guarantee yet. */
412 /* reassociation must run until a fixpoint is reached. */
415 ir_op *op = get_irn_op(n);
416 ir_mode *mode = get_irn_mode(n);
420 /* for FP these optimizations are only allowed if fp_strict_algebraic is disabled */
421 if (mode_is_float(mode) && get_irg_fp_model(current_ir_graph) & fp_strict_algebraic)
424 if (op->ops.reassociate) {
425 res = op->ops.reassociate(&n);
432 wenv->changes |= changed;
435 for (i = get_irn_arity(n) - 1; i >= 0; --i) {
436 ir_node *pred = get_irn_n(n, i);
438 if (get_irn_link(pred) != wenv->wq) {
439 waitq_put(wenv->wq, pred);
440 set_irn_link(pred, wenv->wq);
445 } /* do_reassociation */
448 * Returns the earliest were a,b are available.
449 * Note that we know that we know that a, b both dominate
450 * the block of the previous operation, so one must dominate the other.
452 * If the earliest block is the start block, return curr_blk instead
454 static ir_node *earliest_block(ir_node *a, ir_node *b, ir_node *curr_blk) {
455 ir_node *blk_a = get_nodes_block(a);
456 ir_node *blk_b = get_nodes_block(b);
459 /* if blk_a != blk_b, one must dominate the other */
460 if (block_dominates(blk_a, blk_b))
464 if (res == get_irg_start_block(current_ir_graph))
467 } /* earliest_block */
470 * Checks whether a node is a Constant expression.
471 * The following trees are constant expressions:
473 * Const, SymConst, Const + SymConst
475 * Handling SymConsts as const might be not a good idea for all
478 static int is_constant_expr(ir_node *irn) {
481 switch (get_irn_opcode(irn)) {
486 op = get_irn_op(get_Add_left(irn));
487 if (op != op_Const && op != op_SymConst)
489 op = get_irn_op(get_Add_right(irn));
490 if (op != op_Const && op != op_SymConst)
496 } /* is_constant_expr */
499 * Apply distributive Law for Mul and Add/Sub
501 static int reverse_rule_distributive(ir_node **node) {
503 ir_node *left = get_binop_left(n);
504 ir_node *right = get_binop_right(n);
505 ir_node *x, *blk, *curr_blk;
506 ir_node *a, *b, *irn;
510 if (! is_Mul(left) || !is_Mul(right))
513 x = get_Mul_left(left);
515 if (x == get_Mul_left(right)) {
516 /* (x * a) +/- (x * b) */
517 a = get_Mul_right(left);
518 b = get_Mul_right(right);
520 } else if (x == get_Mul_right(right)) {
521 /* (x * a) +/- (b * x) */
522 a = get_Mul_right(left);
523 b = get_Mul_left(right);
527 x = get_Mul_right(left);
529 if (x == get_Mul_right(right)) {
530 /* (a * x) +/- (b * x) */
531 a = get_Mul_left(left);
532 b = get_Mul_left(right);
534 } else if (x == get_Mul_left(right)) {
535 /* (a * x) +/- (x * b) */
536 a = get_Mul_left(left);
537 b = get_Mul_right(right);
543 curr_blk = get_nodes_block(n);
545 blk = earliest_block(a, b, curr_blk);
547 dbg = get_irn_dbg_info(n);
548 mode = get_irn_mode(n);
551 irn = new_rd_Add(dbg, current_ir_graph, blk, a, b, mode);
553 irn = new_rd_Sub(dbg, current_ir_graph, blk, a, b, mode);
555 blk = earliest_block(irn, x, curr_blk);
556 irn = new_rd_Mul(dbg, current_ir_graph, blk, irn, x, mode);
561 } /* reverse_rule_distributive */
564 * Move Constants towards the root.
566 static int move_consts_up(ir_node **node) {
569 ir_node *l, *r, *a, *b, *c, *blk, *irn, *in[2];
573 l = get_binop_left(n);
574 r = get_binop_right(n);
576 /* check if one is already a constant expression */
577 if (is_constant_expr(l) || is_constant_expr(r))
580 dbg = get_irn_dbg_info(n);
582 if (get_irn_op(l) == op) {
583 a = get_binop_left(l);
584 b = get_binop_right(l);
586 if (is_constant_expr(a)) {
589 blk = get_nodes_block(l);
590 dbg = dbg == get_irn_dbg_info(l) ? dbg : NULL;
592 } else if (is_constant_expr(b)) {
595 blk = get_nodes_block(l);
596 dbg = dbg == get_irn_dbg_info(l) ? dbg : NULL;
599 } else if (get_irn_op(r) == op) {
600 a = get_binop_left(r);
601 b = get_binop_right(r);
603 if (is_constant_expr(a)) {
606 blk = get_nodes_block(r);
607 dbg = dbg == get_irn_dbg_info(r) ? dbg : NULL;
609 } else if (is_constant_expr(b)) {
612 blk = get_nodes_block(r);
613 dbg = dbg == get_irn_dbg_info(r) ? dbg : NULL;
620 /* check if a+b can be calculted in the same block is the old instruction */
621 if (! block_dominates(get_nodes_block(a), blk))
623 if (! block_dominates(get_nodes_block(b), blk))
629 mode = get_mode_from_ops(in[0], in[1]);
630 in[0] = optimize_node(new_ir_node(dbg, current_ir_graph, blk, op, mode, 2, in));
632 if (op == op_Add || op == op_Sub) {
633 reverse_rule_distributive(&in[0]);
637 mode = get_mode_from_ops(in[0], in[1]);
638 irn = optimize_node(new_ir_node(dbg, current_ir_graph, blk, op, mode, 2, in));
643 } /* move_consts_up */
646 * Apply the rules in reverse order, removing code that was not collapsed
648 static void reverse_rules(ir_node *node, void *env) {
649 walker_t *wenv = env;
650 ir_mode *mode = get_irn_mode(node);
653 /* for FP these optimizations are only allowed if fp_strict_algebraic is disabled */
654 if (mode_is_float(mode) && get_irg_fp_model(current_ir_graph) & fp_strict_algebraic)
658 ir_op *op = get_irn_op(node);
661 if (is_op_commutative(op)) {
662 wenv->changes |= res = move_consts_up(&node);
664 if (op == op_Add || op == op_Sub) {
665 wenv->changes |= res = reverse_rule_distributive(&node);
671 * do the reassociation
673 void optimize_reassociation(ir_graph *irg)
676 irg_loopinfo_state state;
678 assert(get_irg_phase_state(irg) != phase_building);
679 assert(get_irg_pinned(irg) != op_pin_state_floats &&
680 "Reassociation needs pinned graph to work properly");
682 /* reassociation needs constant folding */
683 if (!get_opt_reassociation() || !get_opt_constant_folding())
686 /* we use dominance to detect dead blocks */
690 * Calculate loop info, so we could identify loop-invariant
691 * code and threat it like a constant.
692 * We only need control flow loops here but can handle generic
693 * INTRA info as well.
695 state = get_irg_loopinfo_state(irg);
696 if ((state & loopinfo_inter) ||
697 (state & (loopinfo_constructed | loopinfo_valid)) != (loopinfo_constructed | loopinfo_valid))
698 construct_cf_backedges(irg);
701 env.wq = new_waitq();
703 /* now we have collected enough information, optimize */
704 irg_walk_graph(irg, NULL, wq_walker, &env);
705 do_reassociation(&env);
707 /* reverse those rules that do not result in collapsed constants */
708 irg_walk_graph(irg, NULL, reverse_rules, &env);
710 /* Handle graph state */
712 set_irg_outs_inconsistent(irg);
713 set_irg_loopinfo_inconsistent(irg);
717 } /* optimize_reassociation */
719 /* Sets the default reassociation operation for an ir_op_ops. */
720 ir_op_ops *firm_set_default_reassoc(ir_opcode code, ir_op_ops *ops)
722 #define CASE(a) case iro_##a: ops->reassociate = reassoc_##a; break
737 } /* firm_set_default_reassoc */
739 /* initialize the reassociation by adding operations to some opcodes */
740 void firm_init_reassociation(void)
742 FIRM_DBG_REGISTER(dbg, "firm.opt.reassoc");
743 } /* firm_init_reassociation */